DMC's whole plot is basically "Dante is bored", isn't it? Wouldn't the Order's whole plan fall apart without the Sparda sword?
Goes a bit beyond him being bored. If you ask me, that applies to the anime, where he seemed so perpetually bored that he seemed miserable.
I believe they needed the Sparda sword, yes. Why Trish gave it to them, I do not know, because I'm pretty sure she brought nothing useful to the good guys by going in undercover. But the Order, oh boy, they got a massive boost.
They did not do a good job with Trish in DMC4...
EDIT: They didn't need the sword? Hm. It has been a while.
~On How To Close Topics - In Memory of callingjaguar~ callingjaguar: tell me how to take it off or i will c*m on you
He killed mundus, the demon king, and defeated/killed his brother, in 3/1 respectively, who was tho only other one who rivaled his skill. After such a track record I don't see a point in taking other demons as a serious threat. Still other demons would rise stronger than mundus, but that was probably the reasoning behind it.
He didn't actually KILL Mundus. Didn't he just seal him away again?
And he was technically serious at a few moments like when Credo gave Dante his last request.